For many individuals in our aging world population, undiagnosed and/or untreatable bone strength losses have weakened these individuals' bones to a point that even normal daily activities pose a significant threat of fracture. In one common scenario, when the bones of the spine are sufficiently weakened, the compressive forces in the spine can cause fracture and/or deformation of the vertebral bodies. For sufficiently weakened bone, even normal daily activities like walking down steps or carrying groceries can cause a collapse of one or more spinal bones. A fracture of the vertebral body in this manner is typically referred to as a vertebral compression fracture. Other commonly occurring fractures resulting from weakened bones can include hip, wrist, knee and ankle fractures, to name a few.
Fractures such as vertebral compression fractures often result in episodes of pain that are chronic and intense. Aside from the pain caused by the fracture itself, the involvement of the spinal column can result in pinched and/or damaged nerves, causing paralysis, loss of function, and intense pain which radiates throughout the patient's body. Even where nerves are not affected, however, the intense pain associated with all types of fractures is debilitating, resulting in a great deal of stress, impaired mobility and other long-term consequences. For example, progressive spinal fractures can, over time, cause serious deformation of the spine (“kyphosis”), giving an individual a hunched-back appearance, and can also result in significantly reduced lung capacity and increased mortality.
Until recently, treatment options for vertebral compression fractures, as well as other serious fractures arid/or losses in bone strength, were extremely limited—mainly pain management with strong oral or intravenous medications, reduced activity, bracing and/or radiation therapy, all with mediocre results. Because patients with these problems are typically older, and often suffer from various other significant health complications, many of these individuals are unable to tolerate invasive surgery. In addition, to curb further loss of bone strength, many patients are given hormones and/or vitamin/mineral supplements—again with mediocre results and often with significant side effects.
In an effort to more effectively and directly treat vertebral compression fractures, minimally invasive techniques such as vertebroplasty and, subsequently, kyphoplasty, have been developed. Both techniques involves the percutaneous injection of a flowable reinforcing material, usually polymethylmethacrylate (PMMA—commonly known as bone cement), into a fractured, weakened, or diseased vertebral body. Shortly after injection, the liquid filling material hardens or polymerizes, desirably supporting the vertebral body internally, alleviating pain and preventing further collapse of the injected vertebral body.
In a vertebroplasty procedure, a needle is inserted directly into a vertebral body, and the bone cement is dispensed from the needle. Because the liquid bone cement naturally follows the path of least resistance within bone, and because the small-diameter needles used to deliver bone cement in vertebroplasty procedure typically require either high delivery pressures to ensure that the bone cement remains within the already compromised vertebral body is a significant concern in vertebroplasty procedures.
Kyphoplasty addresses this issue by first creating a cavity within the vertebral body (e.g., with an inflatable balloon to enable the procedure to be performed percutaneously) and then filling that cavity with bone filler material. The cavity provides a natural containment region that minimizes the risk of bone filler material escape from the vertebral body. An additional benefit of kyphoplasty is that the creation of the cavity can also restore the original height of the vertebral body, further enhancing the benefit of the procedure.
In both vertebroplasty and kyphoplasty procedures (as in any procedure in which filler material is delivered percutaneously to a target location in a body), the ability to apply higher pressures to the filler material can beneficially enhance the safety, efficacy, and/or flexibility of the procedure. For example, the use of higher viscosity bone cements can reduce the likelihood of extravasation, and the use of smaller diameter delivery tools (e.g., cement delivery needles or nozzles) can minimize trauma to the patient and provide greater placement flexibility.
Accordingly, it is desirable to provide surgical tools and techniques that can generate high pressures for use in surgical procedures.